1. Field of the Invention
This invention relates to a method of joining pipes, which is especially suited for joining thin wall metal pipes.
2. Description of the Prior Art
In prior art methods of joining pipes, which can be easily carried out at a factory site, one of two pipes to be joined together is formed with an outwardly tapered joint or a flared end section having an annular gasket or the like. The other pipe is inserted into the tapered joint section thus formed such that it is embraced within the joint section.
In this prior art method, however, the two pipes are joined together along a distance which is substantially equal to the length of the tapered joint section formed on one of the pipes. Therefore, the joint obtained after completion of the joining operation is relatively short and is weak with respect to bending forces and is liable to be bent into a V-shaped form by an external force applied to the joint in a direction normal to the pipe axis.
This bending has been inevitable because of the large lengths of pipes joined together. However, leakage of a fluid or intrusion of water from the outside may occur at the bent joint, so that there has been a need for solving this problem by the formation of a stronger joint.
The present invention is intended to solve the above problem, and it seeks to provide an improved method of joining pipes. An elastic gasket ring and a C-shaped metal ring are provided on the inner surface of a tapered joint section on one of the two pipes to be joined together. The pipe joint section having the tapered portion flares outwardly toward the pipe end. The pipe to be inserted into the flared portion is provided with a generally straight end section adapted to be received within an enlarged section on the pipe having the tapered joint section. This enlarged section is adjacent the inward end of the tapered joint section. The end portion of the pipe to be inserted into the tapered joint section is inserted until the end reaches an engagement portion or stop on the inside of the enlarged section of the flared pipe. Two split die halves having working sections with tapered surfaces are placed face to face such as to embrace a portion of the inserted pipe adjacent to the end thereof and the tapered joint section. The split die halves are moved along the pipe axis toward each other to cause a portion of the tapered joint section adjacent the free end thereof to be plastically deformed by bending or contracting fashion toward the inserted pipe by the axial movement of at least one of the split die halves. This reduction in diameter thereby causes compression of the elastic gasket ring thereby obtaining a seal effect. The reduction in diameter also causes compression of the C-shaped metal ring. The ring is compressed by the inner surface of the bent or contracted portion of the tapered joint section adjacent the end thereof. Thus, the inner diameter of the compressed C-shaped metal ring wedges into the wall of the inserted pipe end and the outer diameter of the compressed C-shaped metal ring engages the now inclined inner surface at the end portion of the tapered joint section.